The purpose of this study is to compare methods of body composition in a heterogeneous group of adult men and women, as measured by underwater weighing, dual energy X-ray absorptiometry, skin folds, and bioelectrical impedance analysis. A total of 50 adult (over 18 years of age) male and female volunteers will be recruited for the study over a five year period (3/1/96 - 2/28/2001). Since the study began approximately two years ago, a total of 27 volunteers have completed the study. We expect to recruit approximately 12 additional volunteers during each of the remaining two years. No preliminary analysis of the data on the first 25 volunteers has, as yet, been completed.